In pending application Ser No. 11/903,261, filed Sep. 21, 2007, titled “Non-Invasive Multi-Function Sensor”, the disclosure of which is incorporated herein by reference, a system is disclosed for measuring various characteristics of a liquid flowing in a tube of a compressible material, such as of plastic. These characteristics can be, for example, one or more of the temperature of the liquid as measured by a temperature sensor, the presence of air bubbles or particles in the liquid as measured by an ultrasonic sensor, and the type of liquid as measured by color determination using an LED. Such a system, or one or more parts of it, is found to be useful in medical and analytical laboratories where, for example, an end user needs to know if air bubbles or particles are present in the liquid. Such a system also could let a user know the presence/absence of a liquid flowing in the tube for fill and empty applications of various liquids and solutions in semi-conductor industries.
The system of the applications uses a measuring head that contains, depending on the application and requirements, one or more of the sensors for making the determination of the characteristic or characteristics of the liquid. The head has a slot in which the tube of compressible material is placed to be confronted by the sensing element or elements of each of the one or more sensors. For example, an ultrasonic sensor used to determine the presence of air bubbles/particles and the presence or absence of liquid in the tube would have two elements such as a piezoelectric crystals, one for transmitting energy through the tube and the other for receiving the energy. These crystals are on opposite walls of the slot in which the tube is placed.
In the measuring head of the system as described in the application it has been determined that it would be advantageous to provide an arrangement for positively holding or locking the tube in the slot. This is of importance while measurement of the liquid characteristics is taking place to prevent the tube from becoming displaced from the slot if the head out to is accidentally moved. It is preferred that such a positive locking arrangement be simple and easy to use and also inexpensive in its construction.